Internal combustion engine designers typically desire to minimize the outer dimensions of the engine consistent with achievement of other design objectives such as adequate strength and power characteristics. Thus, each cylinder is placed as close as possible to its adjacent cylinder and the various components that accompany each cylinder are also compactly arranged. In engines employing cam driven injectors, three separate cam follower assemblies are generally used for each cylinder and must be mounted to convert the rotational movement of corresponding cams into reciprocal movement of a corresponding intake valve, exhaust valve, or injector by means of associated drive trains. Because the cam follower assemblies and their associated mounting structures are subject to high stresses during engine operation, compromises must be made between achieving a rugged, high strength construction and maintaining the overall size within acceptable limits.
Even a simple cam follower assembly mounting scheme, such as illustrated in U.S. Pat. No. 4,326,484 to Amrhein, imposes size limitations on the amount of space within the engine which can be assigned to each cam follower. In particular, each cam follower assembly, designed in accordance with the Amshein '484 patent, includes a roller engaging a corresponding cam mounted on the camshaft and a tappet body mounted for reciprocal movement in the adjacent support structure of the engine block. The tappet body includes a pair of legs for receiving a pin extending through the center of the roller and passing into receiving bores in the legs of the tappet body and thus, the thrust forces imparted by the roller must be borne by the legs of the tappet. However, to accommodate the transmitted thrust, the legs and pin must have a relatively substantial axial dimension. In a like manner, the supporting structure surrounding each cam follower tappet body must be sufficiently strong to restrict the associated cam follower to its predetermined path of travel. To adequately perform this function, the surrounding structure must be allotted some of the available axial space thereby further restricting the axial distance which may be occupied by each roller.
Another type of cam follower design known to the prior art includes a link pivotally connected at one end to the engine block and provided at the other end with a pin mounted, cam engaging roller. An example of such a cam follower is disclosed in U.S. Pat. No. 4,369,627 but this type of design does not eliminate the length constraints imposed on the roller by the need to provide thrust conveying legs to receive the ends of the roller supporting pin.
It is also known in the art to use pinless rollers to transmit the force of a rotatable cam to a drive train in an internal combustion engine. Church U.S. Pat. No. 1,565,223 (element 21), Wood, Jr. U.S. Pat. No. 2,508,557 (element 4), Clouse U.S. Pat. No. 3,822,683 (element 32), and Metzen U.S. Pat. No. 4,204,814 (element 4) disclose pinless rollers used in cam followers or similar assemblies. However, these references do not suggest how pinless rollers can be used to reduce overall engine size.
Although the prior art is replete with various types of cam follower assemblies, heretofore there has not been an assembly that combines the beneficial features of a rotatable cam follower link with the advantages of a pinless roller to allow the rollers in a given set of cam followers serving each cylinder to occupy the maximum portion of the total axial length which may be assigned to the set of cam followers. None of the known assemblies uses a pinless roller and pivotal link to maximize the total force transmitting capacity of the assembly having a predetermined width while maintaining cam surface stresses within acceptable limits. None of the prior art discloses how a simple cam follower link combined with a pinless roller held in place by axial end walls can assist in achieving improved engine performance without increased size.